Visceral fat increases risk of colon cancer

According to an animal study published in Cancer Prevention Research, visceral fat may be directly linked to an increased risk for colon cancer.

"There has been some scepticism as to whether obesity per se is a bona fide cancer risk factor, rather than the habits that fuel it, including a poor diet and a sedentary lifestyle," said Dr Derek M Huffman, postdoctoral fellow at the Institute for Aging Research at the Albert Einstein College of Medicine, New York. "Although those other lifestyle choices play a role, this study unequivocally demonstrates that visceral adiposity is causally linked to intestinal cancer."

Previous research has shown that obesity increases the likelihood of being diagnosed with and dying from many cancers. Huffman and colleagues investigated whether removing visceral fat in mice genetically prone to developing colon cancer might prevent or lessen the development of these tumours.

The researchers randomly assigned the mice to one of three groups:

Group 1 - mice underwent a sham surgery and were allowed to eat an unrestricted "buffet-style" diet, for the entirety of the study, which resulted in these mice becoming obese.

Group 2 - mice were also provided an unrestricted diet and became obese, but they had their visceral fat surgically removed at the outset of the study.

Group 3 - mice also underwent a sham surgery, but were provided only 60% of the calories consumed by the other mice in order to reduce their visceral fat by dieting.

Huffman said that the sham-operated obese mice had the most visceral fat, developed the greatest number of intestinal tumours, and had the worst overall survival.

However, the mice that had lower levels of visceral fat, either due to a low-calorie diet or surgical removal, had fewer intestinal tumours.

Huffman said: “This was particularly remarkable in the case of our group where visceral fat was surgically removed, because these mice were still obese, they just had very little abdominal fat.

The researchers then subdivided the groups by gender. In female mice, the removal of visceral fat was significantly related to a reduction in intestinal tumours, but calorie restriction was not. In male mice, calorie restriction had a significant effect on intestinal tumours, but removal of visceral fat did not.

"This suggests that there are important gender differences in how adiposity and nutrients interact with the tumour environment," said Huffman.

The researchers stressed that more studies are needed to discover the mechanisms behind the causality between visceral fat and intestinal cancer, to determine how abdominal obesity and nutrient availability act independently during the stages of tumour promotion and progression, and examine determine how other strategies to promote weight loss, such as bariatric surgery, affect cancer risk.

They concluded that their study shows that strategies designed to reduce visceral adiposity stores in humans should be considered in the prevention of intestinal cancer.

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